Climate, Land Management and Future Wildlife Habitat in the Pacific Northwest

Currently the Bureau of Land Management (BLM) is revising its regional resource management plans for five districts in Oregon including Medford, Coos Bay, Roseburg, Salem and Eugene. Resource management plans outline how the bureau will protect areas of critical concern, including habitat for threatened and endangered species, while also supporting recreation, mining and grazing on public lands.

For Terry Fairbanks, a district silviculturist for BLM, an important unknown that complicates planning is the future distribution of moist and dry forest. Moist forests are currently most common in western Washington and northwestern Oregon. These are the forests that, if left undisturbed by fire or human activity, would eventually be dominated by hemlock, although they may now contain mostly Douglas-fir. In contrast, dry forests, like those of southern Oregon, tend to be a mix of Douglas-fir, ponderosa pine and various hardwoods like oak in the lower elevations and mostly white fir in the higher elevations.

As climate change brings drier summers and more wildfires to the Northwest, moist forests are expected to be replaced by dry forests further north. This may mean more work to manage because dry forests require more activities like thinning to keep them resilient to fire and useful as habitat for species like the northern spotted owl.

As Fairbanks prioritizes restoration and other treatments she wants to understand how climate will affect future vegetation. As she puts it “This is a massive area that could benefit. We need to know what kind of forest we’re working with because we don’t want to waste our time.”

Luckily for Fairbanks, Emilie Henderson has been adapting computer models to help illustrate how climate change will affect Southwest Oregon’s forests. Henderson is the Ecological Modeling Team Lead at Oregon State University’s Institute for Natural Resources. Henderson is working closely with her colleagues, Jessica Halofsky of the University of Washington and Megan Creutzburg of Oregon State University in an effort to incorporate information from global climate models, process-based models, specific vegetation models and human activities to look at the interactive effects of climate and management.

That’s a long list of variables and it leads to “a lot of boxes and arrows that end up looking like a big plate of spaghetti and meatballs,” says Henderson, “but when you get down to the nitty gritty, and sit down with someone who has plenty of on-the-ground experience, but little or no computer modeling experience, you can actually talk to them in a functional way about how the models work, which is really cool.”

The important innovation of the team’s modeling approach is that it allows shifts in vegetation type to occur. As Halofsky explains, other models “allow for shifts within a specific vegetation type, but not among them.” The new models develop a picture of existing conditions from potential vegetation (based on ecotype), current vegetation (based on detailed vegetation maps developed by Forest Service) and an “owner allocation grid” (based on who owns the land and how they are likely to manage it). It incorporates onto that a suite of relatively predictable changes- things like tree growth, timber harvest, disease outbreaks and wildfire as well as changes projected from global climate models.

The end result is what Henderson refers to as a “science-based story telling mechanism- or story-comparing mechanism.” She points out that, although the models cannot be used to predict things like the precise number of acres of northern spotted owl habitat that will be present in the future, they are still useful tools. “A good way to use our results instead,” she explains “is for comparing management approach X with management approach Y to find out that in 20 years management approach Y seems to be better for owls.”

With support from the Northwest Climate Science Center, Henderson and her team have applied their approach to spotted owl habitat in coastal Washington and Southwest Oregon and to sage grouse habitat in southeast Oregon. Their results are currently being used to inform management planning, not only by BLM but also by USDA Forest Service and The Nature Conservancy.

For managers like Fairbanks, Henderson’s advances in modeling are very welcome. This tool helps prioritize restoration investments in habitats with the highest chance of existing in the future and also helps identify how best to build resilience in areas that are the most likely to change.

The recent publication in AIMS Environmental Science by Megan Creutzburg, Emilie Henderson and David Conklin titled “Climate change and land management impact rangeland condition and sage-grouse habitat in southeastern Oregon.”

The chapter titled “Using a dynamic global vegetation model to help inform management decisions” in a recently published book about the MC1 dynamic global vegetation model edited by Dominique Bachelet and David Turner.

This study addressed the challenges faced by natural resource management planning in the context of climate change. We explored how future climate may interact with management alternatives to shape wildlife habitat across large landscapes. We studied habitat for the northern spotted owl in coastal Washington and southwestern Oregon, and habitat for the greater sage-grouse in southeastern Oregon. In coastal Washington, the primary threat to owl habitat is likely to be habitat loss as a result of increasing fire and shifts in vegetation with changing climate. These threats may not be fully mitigated with management. In southwest Oregon, increasing fire frequencies under climate change are also likely to pose the greatest threat to owl habitat. Management aimed at constraining fires is needed, but due to the scope of the problem, strategic fuel treatment management will be vital. In southeast Oregon, some threats to sage-grouse habitat are more manageable than others. Wildfire increased under all climate scenarios. Climatic constraints to sage-grouse from hotter, drier summers cannot be managed, but some effects of climate change may aid the goals of management. For instance, increasing fire frequency can help control juniper expansion. Unfortunately, invasive annual grasses are poised to invade much of the landscape at a rate that could exceed the capacity of management. While the task of maintaining and enhancing habitat across large, complicated landscapes in the face of climate change is daunting, this research yields information that is useful in setting management priorities and developing strategies for maintaining habitat and addressing other major goals in all three regions.

Control invasive plant species: Invasive vegetation encroachment is predicted to increase at alarming rates in the future due to climate change. This project evaluated the value of increasing the frequency and magnitude of invasive species removal.

Mitigate wildfire where possible: This project also evaluated the likely impacts of strategic fuel treatment management to mitigate the effects of projected increases in wildfire.